mozilla/pdf.js · error · Error

mapCidRange - ignoring data above MAX_MAP_RANGE.

Error message

mapCidRange - ignoring data above MAX_MAP_RANGE.

What it means

Thrown by CMap.mapCidRange when a single cidrange operator spans more than MAX_MAP_RANGE (2^24 - 1 = 16,777,215) code points. The cap prevents the _map array from being expanded into gigabytes of memory by one oversized range. It indicates the CMap (usually embedded in a PDF font) is malformed or actively hostile.

Source

Thrown at src/core/cmap.js:227

    // Map entries have one of two forms.
    // - cid chars are 16-bit unsigned integers, stored as integers.
    // - bf chars are variable-length byte sequences, stored as strings, with
    //   one byte per character.
    this._map = [];
    this.name = "";
    this.vertical = false;
    this.useCMap = null;
    this.builtInCMap = builtInCMap;
  }

  addCodespaceRange(n, low, high) {
    this.codespaceRanges[n - 1].push(low, high);
    this.numCodespaceRanges++;
  }

  mapCidRange(low, high, dstLow) {
    if (high - low > MAX_MAP_RANGE) {
      throw new Error("mapCidRange - ignoring data above MAX_MAP_RANGE.");
    }
    while (low <= high) {
      this._map[low++] = dstLow++;
    }
  }

  mapBfRange(low, high, dstLow) {
    if (high - low > MAX_MAP_RANGE) {
      throw new Error("mapBfRange - ignoring data above MAX_MAP_RANGE.");
    }
    const lastByte = dstLow.length - 1;
    while (low <= high) {
      this._map[low++] = dstLow;
      // Only the last byte has to be incremented (in the normal case).
      const nextCharCode = dstLow.charCodeAt(lastByte) + 1;
      if (nextCharCode > 0xff) {
        dstLow =
          dstLow.substring(0, lastByte - 1) +

View on GitHub (pinned to 5903d58d58)

Solutions

1. Open the PDF in an authoritative reader; if it also fails, the CMap is corrupt - regenerate the PDF or the font subset.
2. Update pdf.js; newer versions handle oversized ranges more gracefully in some code paths.
3. If you control the PDF pipeline, split each cidrange into multiple ranges no wider than 0xFFFFFF.
4. Wrap CMap loading in try/catch and degrade (skip ToUnicode / fall back to a replacement font).

Example fix

// before
const cmap = await CMapFactory.create({ encoding, fetchBuiltInCMap, useCMap });

// after
let cmap;
try {
  cmap = await CMapFactory.create({ encoding, fetchBuiltInCMap, useCMap });
} catch (e) {
  if (/MAX_MAP_RANGE/.test(e.message)) {
    console.warn('Oversized CMap cid range, skipping', e);
    cmap = null;
  } else throw e;
}

try {
  cmap = await CMapFactory.create({ encoding, fetchBuiltInCMap, useCMap });
} catch (e) {
  if (/MAX_MAP_RANGE/.test(e.message)) {
    console.warn('Oversized cid range in CMap, skipping', e);
    cmap = null; // degrade: no CID mapping for this font
  } else {
    throw e;
  }
}

When it happens

Trigger: Parsing a CMap whose begincidrange ... endcidrange block declares a line <low> <high> <dst> where high - low > 0xFFFFFF. Triggered while resolving a CID font's encoding during text extraction or rendering.

Common situations: Corrupted or hand-edited CID-keyed font CMap; a fuzzed or malicious PDF crafted to exhaust memory; a buggy font-subsetting tool that emits one giant range instead of many small ones.

Related errors

• mapBfRange - ignoring data above MAX_MAP_RANGE.
• mapBfRangeToArray - ignoring data above MAX_MAP_RANGE.
• Malformed CMap: expected string.
• Malformed CMap: expected int.
• Invalid bf range.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/720115716918fbaf. Report an issue: GitHub.